An internal electric potential of a substance has been used as a source of phase change in phase plates of electron microscopes. However, when electrons pass through a substance, electron scattering occurs, causing an electron beam loss in image formation and deterioration of image intensity. To alleviate this effect, using a light element (for example, carbon) as a phase plate has been suggested (Japanese Patent Applications Laid-open Nos. 2001-273866 and 2003-100249). However, this suggestion also failed to prevent the occurrence of electron beam loss and lacked utility at an accelerating voltage of 100 kV or less. It was also suggested to prevent the electron beam loss by producing spatially an electrostatic potential (Japanese Patent Application Laid-open No. 9-237603, German Patent Application Laid-open No. 01052965) or a vector potential (Japanese Patent Application Laid-open No. S60-7048) and preventing the loss caused by substance scattering, but these methods have not yet reached the stage of practical use due to difficulties associated with the production process.